The present invention relates to an anti-roll rake device for use in conjunction with a device such as a microtome for cutting frozen samples and to prevent the cut samples from rolling.
In the medical field it is often desired to cut thinly sliced tissue samples for testing or viewing under a microscope. Various devices are known for making such samples, such as razor blades and more specialized instruments. Accurate sample cuts are often required and typically require the use of a microtome instrument.
Various forms of microtomes are known. In general, a microtome is an instrument for cutting thin tissue sections. The sections can be stained for later study under a microscope. One such microtome is the TISSUE-TEK.RTM. Microtome/Cryostat which was manufactured by Miles Inc., Diagnostic Division, Elkhart, Ind. In such a microtome, the tissues to be sampled are prepared for cutting by being embedded in a supportive matrix and then frozen solid. The frozen matrix and embedded tissue are cut with a sharp blade to produce thin sections, which can then be stained and placed on a microscope slide and subsequent viewing under a microscope.
The nature of the slicing process causes the cut section to roll tightly almost immediately after leaving the sharp edge of the cutting blade. Even with the various known anti-roll devices, the cut section still has a structural memory of the rolling, and a tendency to roll or curl after removal from the device.
Various anti-roll devices are known. One such apparatus is an anti-roll plate, as illustrated in U.S. Pat. No. 4,472,989. The anti-roll plate may be a plastic surface. The anti-roll plate is positioned adjacent to the surface of the blade, with a slight gap therebetween. The sample section is expected to pass through the gap between the blade and the anti-roll plate. The gap between the anti-roll plate and blade typically is set to correspond to the thickness of the sample piece to be cut. If the thickness of the sample piece is increased, the gap must also be increased. In other anti-roll plates, the gap is situated between the tissue block to be cut and the plate.
The known anti-roll plates and corresponding techniques suffer the disadvantage of a high proportion of cut sections which get caught on the anti-roll plate, or elsewhere within the gap between the blade and therefore become tainted or unusable. A further disadvantage is that the selection of the width of the gap between the anti-roll plate and blade requires skill and discretion. In addition, dexterity is required to accurately remove the cut section.
Yet a further disadvantage of the anti-roll plate is that the cut tissue section tends to curl or roll after the anti-roll plate is lifted in order to gain access to the cut section. In addition, in typical commercial embodiments, the anti-roll plate is mounted in front of the blade holder and tends to reduce the freedom of access to the cut section. This impairs the ability to readily access the cut section with a glass microscope slide.
Another known technique and apparatus for countering the tendency of thinly sliced tissue sections to roll or curl makes use of a brush. The brush is positioned to catch the leading edge of a tissue section as it passes the blade. This suffers similar disadvantages as discussed above, including requiring operator dexterity and therefore being highly technique dependent. In addition, the operator typically is required to manually guide the brush, during the cutting process. Furthermore, if the brush drags on the cutting surface of the blade, some of the brush bristles may be cut off, potentially contaminating the tissue sample, dulling the blade and reducing the brush size.
Furthermore, the known devices and techniques suffer the disadvantages of requiring slow cutting speeds in order to prevent rolling.
Other such anti-roll devices, which rely on the use of gaps between the blade and device are discussed in U.S. Pat. No. 4,024,779. These devices suffer the same disadvantages as those described above.
It is readily appreciated that there is a substantial need for an anti-roll device that does not rely on operator dexterity or guiding the sample slice between a blade or tissue sample and an anti-roll device.